I think I'm ok. This is no different that a table with contact info, name, address, e-mail etc. Some fields are blank, some get updated with new information, and a lot of data can be updated with one update action. The slides are as unique as a first name, last name, email. You wouldn't necessarily want to store every field in a contact form in a separate table. You may want to store address information, phone numbers, or business information in separate tables that are joined together, but this project's design specifications made a single table for all galleries look like the best idea.
The design limits of 15 images are forced by legal requirements. Slide 1 in Gallery 1, 5, 7, and 23 may be image 1, a photo of Plant 1's production line. Image 5 may be of Data Plate A from Machine Room G taken last march and image 240 may be of Data Plate A from Machine Room G taken yesterday. Gallery 10 is for Machine Room G and Slide 4 is for Data Plate A. When the gallery is updated you replace the image for Slide 4 in Gallery 10 with image 240 from a UI that shows all images in their appropriate slots and a catalogue that is searchable for all images from Machine Room G. I have to make this very easy for a user with an iPad or a smart phone to take images and update the gallery for that particular project. I've built an app that uploads the images and field data to the database.
90% of all galleries contain all 15 images. Updates are made, in some cases, daily. New record sets of specific images for each piece of equipment on the line are created every time a change is made. This is why I wanted one table with slots for each piece of data. It also allows you to create an entire gallery with one insert record action.
A mod log is set up for every action on this Intranet website that records every action in the database so that any archival records from any configuration of the gallery, or any other table, can be instantly called up by simply entering a date. It seems to me that the table you suggested would be far more complex to query for audit history. It also seems like it would take far more effort (mouse clicks) for a user to insert images to a gallery.
I don't know of a way to add multiple rows to a table with one insert or one update action. If one exists that would really help the next project I'm developing.
Thanks again for looking at my problem and making suggestions. You have given me a lot to think about.